#2760 How to get grid to front?

[theozh]

It seems a simple task cannot be realized although gnuplot offers several options:

How to bring the grid in front of the key/legend?
(let's aside whether the grid through the legend helps readability)
(triggered by this question: https://stackoverflow.com/q/79357685)

1. most obvious: set grid front
   The legend does still white out the grid around the area of the legend

2. additionally: set key noopaque
   key still isn't transparent, what you would expect

3. additionally: set term pngcairo transparent background
   Ususally, key box is filled with background color, but setting transparent background color doesn't seem to work

4. set key fc rgb 0xff123456
   transparent color to fill the legend box doesn't seem to work

Tested with Windows10 gnuplot 6.0.2
Just for better visibility of the issue: set grid lt -1

Script:

### how to bring grid to front?
reset session

set xtics 1
set mytics 2
set grid x,y,mx,my front lt -1
set key font ",16" noopaque

plot sin(x), cos(x)
### end of script

[Ethan Merritt]

1) 2)
The key area is intentionally reserved so that the grid will not obscure the key contents. When grid lines are drawn, they are clipped against the key area. So it doesn't matter whether the grid is in front or in back; either way it will not obscure the key. That was a design decision made sometime last century, prior to version 3.7.

3)
You can use the terminal background as a fillcolor for at least some terminal types, as in the sequence below.

set term wxt background "cyan"
set obj rect behind from graph 0,0 to graph 1,1 fillcolor "white"
set key opaque fillcolor background
plot sin(x)

It may be true that the pngcairo terminal doesn't store an alpha channel for the background color (I haven't looked into that) but if so that doesn't really have anything to do with the key area.

4)
The command is set key opaque fillcolor <whatever>

[theozh]

Thanks, Ethan! So, in summary: it is not intended to put the grid in front of the legend. Actually, it is prevented by design.